The present invention relates to drill assemblies, and particularly to components used to direct or distribute operating fluid within drill assemblies having one or more fluid-operated pistons.
One type of commercial drill, commonly referred to as a “down-hole” drill due to its intended application, is typically actuated by high pressure “operating” fluid (e.g., compressed air) that is appropriately directed in order to reciprocate a piston to repetitively impact against a drill bit. These fluid-operated drills may be provided with one of several known systems for supplying and exhausting operating fluid into and out of specific interior fluid chambers used in the operation of the drill. Certain fluid-actuated drills, such as those commercially available from drill manufacturers such as Sandvik, Secoroc and Numa, include a control rod device that interact with holes and ports within the impact piston to deliver and expel air. Other drills, such as those commercially available from Mission, Inc., use ports contained in the outer sleeve or casing of the drill assembly to achieve a similar result.
A third design uses a tubular fluid distributor sleeve or “cylinder” located within the drill outer casing to define a flow path around the operating piston, such as those commercially available from the Ingersoll-Rand Company of New Jersey. More specifically, the distributor cylinder delivers high-pressure air to a first central chamber that supplies air to the interior working chamber(s) of the drill. The cylinder design, while avoiding the shortcomings associated with the need for ports in the piston or casing, does require a means for positioning and supporting the cylinder within the casing.
Precision co-axial alignment requirements, along with holding forces needed to accommodate aggressive shock and vibration loads associated with percussive drilling, requires the supporting and positioning means for the cylinder to be precise, robust and reliable. Axial and radial position must be maintained while holding forces must be large to prevent vibration, movement and resultant wear that could result in misalignment.
Typically, a means for positioning the cylinder within the drill casing employs a separate ring to retain the cylinder at a specified position within the casing, an example of which is also disclosed in U.S. Pat. No. 5,325,926 of Lay et al. Clamping loads applied to the cylinder are transmitted through shoulders on the cylinder, ring and into the casing. The inside shoulder of the ring carries the cylinder load and the outside shoulder of the ring carries the casing load. Such retaining rings typically have a gap to enable the ring to “collapse” or deflect inwardly to enable the ring to be inserted within a recess in the casing. Such a gap can create uneven loading on the retainer ring, which may cause misalignment of the cylinder under load. Additionally, special tooling required for removal and installation of the ring is often cumbersome and reduces the efficiency of service and repair processes.
In view of the above limitations of known cylinder systems, it would be desirable to provide a means for positioning and retaining a fluid cylinder that utilized less components, did not require special tooling to install and remove from a drill casing, was simpler to manufacture and overcame the other inherent limitations of these previously known systems.